Aircraft: REGIONAL JET CL65; UNDIFFERENTIATED OR OTHER MODEL
Phase of flight: Initial Approach
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Unstabilized Approach

We had been cleared PSK to ROA from south of the airport. At about 20 miles out we had the field insight and we were given a right downwind to Runway 24. I asked my First Officer to confirm with ROA Approach that we were cleared the right not left visual approach for Runway 24. ATC confirmed that he needed us to do the right approach. I told my First Officer that I had never done a right traffic pattern to that runway; so I wasn't familiar with a good procedure to get in due to the height of Tinker Mountain (2;407 FT) on downwind that I would try to turn inside of the mountain to turn final. When we got close enough to the terrain I realized that at 160 KTS our turn radius would not allow us to make a safe right turn to final and clear the terrain on the other side of the mountain along with making a stabilized approach. I told my First Officer to ask for a turn out to the left and try to make another turn around Tinker Mountain and then a right turn back in. Again due to the terrain we questioned if we could safely make the turn with the terrain to turn final. We then told Tower that we needed to go way out to the valley and try again. We finally made a safe stabilized approach around Tinker Mountain in the valley. I contacted ATC when I landed because I was frustrated that we were given an approach that a CRJ could never safely make from the south direction. The ATC Supervisor was surprised that we were given that approach and concurred that it was unusual. I wish that my Company would have better policies when coming into airports like this. They should just ban any CRJ from accepting a right downwind to Runway 24. I wish that the ATC had a policy about not clearing certain airplanes for that approach. With our turn radius we can't safely make a traffic pattern unless we stayed at 3;500 FT and over flew the mountain; went into the valley and did a tear drop to turn on final; while at the same time losing visual contact with the airfield. I understand that we have sample approach path charts to take when accepting visuals to Runway 24; however one of them assumes that you are coming in from the north. I also think that it needs to be brought to their attention that turning in from the left downwind for Runway 24 before the mountains is pushing it. Most pilots split the two mountains when doing a visual approach to ensure a better stabilized approach. I also think the Airline needs to ban anyone from doing a visual approach to Runway 16. I was cleared for a visual approach into Runway 16 a few years ago. Due to the rising terrain on base; tight turn to final; and being not stabilized we had to go missed (we circled for Runway 24). I learned a valuable lesson that I can't do a visual to Runway 16 and I can't do a right downwind for the visual to Runway 24. I just hope that some other pilot doesn't have to learn this lesson. A CRJ200 Captain described the complexity of flying a right downwind visual approach to ROA Runway 24 because of Tinker Mountain terrain and suggests the CRJ aircraft turn radius makes the approach unsafe.